1. Field
Example embodiments relate to power devices, and more particularly, to high electron mobility transistors (HEMTs) and methods of manufacturing the same.
2. Description of the Related Art
A high electron mobility transistor (HEMT) includes semiconductors with different band gaps. In a HEMT, semiconductors with different band gaps are joined together. In a HEMT, a semiconductor with a relatively wide band gap functions as a donor. Such a semiconductor with the relatively wide band gap forms 2-dimensional electron gas (2DEG) in a semiconductor with a relatively narrow band gap. In a HEMT, the 2DEG may be used as a channel. As a result, a channel is spatially apart from a donor in a HEMT, and thus electron carriers may have high mobility. A HEMT has a hetero-junction structure, and thus a HEMT is also known as a hetero-junction field effect transistor (HFET).
A HEMT may not only be used for improving the mobility of electron carriers, but may also be used as a transistor with a substantially high breakdown voltage as a power device. A HEMT includes a semiconductor with a relatively wide band gap, (e.g. a compound semiconductor). Therefore, a breakdown voltage of a HEMT may be high.
2DEG may be formed by n-doping a material having a relatively wide band gap or by using a polarized material.
In a semiconductor device, space charge occurs due to depletion. Thus, an electric field may be concentrated at a gate. Similarly, in a HEMT, the 2DEG between a gate and a drain is removed during a turning-off operation, a space charge remains, and an electric field is concentrated at the gate due to the space charge. Due to the concentration of the electric field at the gate, the breakdown voltage of the HEMT may decrease.